Endophytic Bosea spartocytisi sp. nov. Coexists with rhizobia in root nodules of Spartocytisus supranubius growing in soils of Teide National Park (Canary Islands)

Abstract

Two rod-shaped Gram negative strains, SSUT16^T and SSUT22, were isolated from root nodules of Spartocytisus supranubius in soils of the Teide National Park (Tenerife, Spain). The 16S rRNA gene sequences of these two novel strains classified them within genus Bosea with similarity values ranging from 97.65 % to 99.54 % with respect to the other species of this genus. The MLSA analysis from a concatenation of the two housekeeping- genes, recA and gyrB, showed that Bosea thiooxidans LMG 26210^T and B. robiniae LMG 26381^T are the two closest relative species with which they share similarity sequences values of 94.42 % and 94.27 %, respectively. The genome sequence analysis of strain SSUT16^T showed average nucleotide identity percentages (ANIb) and digital DNA-DNA hybridization (dDDH) below 84 % and 33 %, respectively, with the type strains of all sequenced species of genus Bosea. These values are much lower than the currently accepted cut-off values for these two parameters to delineate bacterial species, confirming that the novel strains constitute a novel Bosea species. In addition, they are also distinguished from the other closest species in their fatty acid composition and in other phenotypic characteristics. Genome sequence analysis showed the absence of the common nodulation and nitrogen fixation genes in the novel strains. Therefore, based on the results of phylogenetic, genomic, chemotaxonomic and phenotypic characterization, we propose a new species named Bosea spartocytisi sp. nov., with type strain SSUT16^T (=LMG 32510^T = CECT 30526^T = HAMBI 3759^T).